Primary haemostasis in thyroid disease.

Objectives: There have been reports on a bleeding tendency in hypothyroidism resembling von Willebrand's disease. The aim of the present study was to investigate whether altered primary haemostasis is a general phenomenon in thyroid disease.

Design/setting: A total of 10 patients with hyperthyroidism and nine patients with hypothyroidism were studied at diagnosis, and during treatment with carbimazole or L-thyroxine, respectively, when euthyroidism had been achieved.

Results: In untreated hypothyroidism, template bleeding time was prolonged (median 9.3 min, range 3.8-20.0 min) compared to that in controls (median 4.0 min, range 3.0-6.0 min; P < 0.05), whereas maximal agglutination velocity induced by ristocetin was decreased (38% min-1, range 4-52% min-1 vs. 70% min-1, range 60-81% min-1, P < 0.05). The level of von Willebrand factor antigen in plasma from hypothyroid patients was less than half of the value in hyperthyroid patients. This difference disappeared after euthyroidism was achieved.

Conclusions: We found that changed primary haemostasis is a general feature of hypothyroidism, and that it is resolved after levothyroxine treatment.